## 13.3. Number Registers Used in mm

Table 13-1 lists mm's number registers. A dagger () next to a register name indicates that the register can be set only from the command line or before the mm macro definitions are read by the formatter. Any register having a single-character name can be set from the command line with the `-r` option.

#### Table 13-1. mm Number Registers

Register | Description
--- | ---
`A` | If set to 1, omit technical memorandum headings and provide spaces appropriate for letterhead (see .AF macro).
`Au` | Omit author information on first page (see .AU macro).
`C` | Flag indicating type of copy (original, draft, etc.).
`Cl` | Level of headings saved for table of contents (see .TC macro). Default is 2.
`Cp` | If set to 1 (default), list of figures and tables appear on same page as table of contents. Otherwise, they start on a new page.
`D` | If set to 1, use debug mode (mm continues even after encountering normally fatal errors). Default is 0.
`De` | If set to 1, eject page after each floating display. Default is 0.
`Df` | Set format of floating displays (see .DF macro).
`Ds` | Set space used before and after static displays.
`E` | Font for Subject/Date/From. 0 (bold, the default) or 1 (roman).
`Ec` | Equation counter, incremented for each `.EC` macro.
`Ej` | Heading level for page eject before headings. Default is 0 and no eject.
`Eq` | If set to 1, place equation label at left margin. Default is 0.
`Ex` | Exhibit counter, incremented for each `.EX` macro.
`Fg` | Figure counter, incremented for each `.FG` macro.
`Fs` | Vertical spacing between footnotes.
`H1 ... H7` | Heading counters for levels 1 to 7, incremented by `.H` macro of corresponding level or by `.HU` macro if at level given by register `Hu`. Registers `H2` to `H7` are reset to 0 by any `.H` (or `.HU`) macro at a lower-numbered level.
`Hb` | Level of heading for which break occurs before output of body text. Default is 2.
`Hc` | Level of heading for which centering occurs. Default is 0.
`Hi` | Type of indent after heading. Values are 0 (left-justified), 1 (indented, the default), 2 (indented except after `.H`, `.LC`, `.DE`).
`Hs` | Level of heading for which space after heading occurs. Default is 2.
`Ht` | Numbering type of heading: 1 (single) or 0 (concatenated, the default).
`Hu` | Set level of heading at which unnumbered headings occur. Default is 2.
`Hy` | If set to 1, enable hyphenation. Default is 0.
`L` | Set length of page. Default is 66v.
`Le` | Flag to print list of equations after table of contents: 0 (don't print, the default) or 1 (print).
`Lf` | Like `Le`, but for list of figures.
`Li` | Default indent of lists. Default is 6n for `nroff` and 5n for `troff`.
`Ls` | Set spacing between items in nested lists. Default is 6 (spacing between all levels of list).
`Lt` | Like `Le`, but for list of tables.
`Lx` | Like `Le`, but for list of exhibits.
`N` | Set page-numbering style: 0 All pages get header (the default) 1 Header printed as footer on page 1 2 No header on page 1 3 Section-page as footer 4 No header unless `.PH` has been invoked 5 Section-page and section-figure as footer
`Np` | Set numbering style for paragraphs: 0 (unnumbered, the default) or 1 (numbered).
`O` | Offset of page. For `nroff`, value is unscaled number representing character positions; default is 9 (.75i). For `troff`, value is scaled; default is .5i.
`Oc` | Set numbering style for pages in table of contents: 0 (lowercase roman, the default) or 1 (arabic).
`Of` | Set separator for figure number in captions. 0 (use period, the default); 1 (use hyphen).
`P` | Current page number.
`Pi` | Amount of indent for paragraph. Default is 5n for `nroff` and 3n for `troff`.
`Ps` | Amount of spacing between paragraphs. Default is 3v.
`Pt` | Paragraph type. Values are 0 (left-justified, the default), 1 (indented), 2 (indented except after `.H`, `.LC`, `.DE`).
`Pv` | Suppress “PRIVATE” header by setting to 0 (default).
`Rf` | Reference counter, incremented for each `.RS`.
`S` | Default point size for `troff`. Default is 10. Vertical spacing is `\nS+2`.
`Si` | Standard indent for displays. Default is 5n for `nroff` and 3n for `troff`.
`T` | Type of `nroff` output device. Sets registers for specific devices.
`Tb` | Table counter, incremented for each `.TB`.
`U` | Style of `nroff` underlining for `.H` and `.HU`. If not set, use continuous underline; if set, don't underline punctuation and whitespace. Default is 0.
`W` | Width of page (line and title length). Default is 6i.

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